Does a light aircraft pilot need a deviation card?
Do we need to swing the compass regularly?
Do we need to know that the compass, although quite accurate, is not perfect?
Three very different questions! My vote is no, yes, yes respectively.
I agree that it's awkward trying to work out whether the pitot heat should be on! So why not scrap the conventional deviation card, and replace it with a similar card with two things written on it - the date of the last compass swing, and whether pitot heat should be on or off.
Cheers,
O8